The recent development of HD (High Definition) broadcasting equipment has enabled imaging apparatuses integrated with VTRs, so-called camcorders to have an image whose vertical resolution is nearly twice that of an image obtained with a field frequency of 60 Hz according to an interlace scanning system which is a standard television system. In response to high-quality images achieved thus by the imaging apparatuses integrated with VTRs, film shooting and so on have become active using the imaging apparatuses integrated with VTRs.
An imaging apparatus such as the imaging apparatus integrated with a VTR performs photographing according to the progressive scanning system with a frame frequency of 24 Hz in such a manner as to photograph 24 still-frame pictures/second like a 24 exposure film camera (e.g., Japanese Patent Laid-Open No. 2002-152569).
Further, such an imaging apparatus is configured so that an imaging signal obtained by the progressive scanning system with a frame frequency of 24 Hz (hereinafter referred to as a 24p imaging signal) is subjected to 2:3 pull-down processing, the signal is converted into an image signal obtained with a field frequency of 60 Hz by the interlace scanning system which is a standard television system (hereinafter referred to as a 60i signal), and the image signal is recorded in a video tape. The imaging apparatus is configured thus for the following advantage: the conversion into the 60i signal allows a recording section to have a conventional configuration. Further, a display section such as an external monitor and a VF (view finder) for confirming a recorded image on the spot also can be configured in a conventional manner. Therefore, it is not necessary to develop a recording section and a display section for the progressive scanning system, thereby reducing the price. A so-called 2:3 pull-down signal obtained by the conversion into the 60i signal by the 2:3 pull-down processing can be converted into a signal with a frame frequency of 24 Hz according to the progressive scanning system by performing so-called 2:3 reverse pull-down processing.
The following will describe a conventional imaging apparatus capable of recording a 24p imaging signal. FIG. 15 is a block diagram showing the configuration of the imaging apparatus.
In FIG. 15, reference numeral 1 denotes a lens section. The lens section 1 is constituted of a lens of an optical system, an optical aperture, a mechanical shutter or an electronic shutter, and so on. Reference numeral 2 denotes an imaging section. The imaging section 2 is constituted of a CCD (Charge Coupled Device). Further, the imaging section 2 transfers accumulated charge by progressive scanning and outputs a 24p imaging signal every ( 1/24) second.
Reference numeral 3 denotes a memory section. The memory section 3 writes a 24p imaging signal in a memory area (not shown), performs 2:3 pull-down processing to convert the signal into a 60i signal of the standard television system, and outputs a so-called 2:3 pull-down signal. That is, an odd-numbered line (odd) and an even-numbered line (even) of an interlace signal are alternately outputted from the memory section 3 every ( 1/60) second.
Reference numeral 4 denotes a recording section. The recording section 4 generates a video signal which is obtained by adding a 60i vertical synchronizing signal (60i--SYNC) of the 60i signal to the 2:3 pull-down signal from the memory section 3, and the recording section 4 records the video signal in a recording medium such as a videotape.
Reference numeral 5 denotes a display section such as a VF. The display section 5 generates a display signal which is obtained by adding the 60i vertical synchronizing signal (60i--SYNC) of the 60i signal to the 2:3 pull-down signal from the memory section 3, and the display section 5 displays the display signal.
Reference numeral 6 denotes a synchronizing signal generating section. The synchronizing signal generating section 6 generates a vertical synchronizing signal for a 24p imaging signal (hereinafter referred to as a 24p vertical synchronizing signal) and a vertical synchronizing signal for a 60i signal (hereafter referred to as a 60i vertical synchronizing signal).
Reference numeral 7 denotes a photographed image state detecting section. The photographed image state detecting section 7 detects a state of a photographed image and outputs a control signal to the lens section 1 and the imaging section 2.
Referring to FIGS. 15 and 16, the following will describe the operations of the imaging apparatus thus configured. FIG. 16 is a diagram for explaining the operations of the imaging apparatus and shows the signal states and operations of (a) to (d) and (f) to (k) shown in FIG. 15.
FIG. 16(a) shows the output timing of the 24p imaging signal.
FIGS. 16(b) and 16(c) show the outputting operations of the 24p imaging signal by the imaging section 2.
FIG. 16(d) shows the 24p vertical synchronizing signal.
FIG. 16(f) shows a detecting operation of a state of a photographed image for the 24p imaging signal, the state being detected by the photographed image state detecting section 7.
FIG. 16(g) shows an outputting operation of a control signal by the photographed image state detecting section 7.
FIG. 16(h) shows the 60i vertical synchronizing signal.
FIG. 16(i) shows a writing operation of the memory section 3.
FIG. 16(j) shows a reading operation of the memory section 3.
FIG. 16(k) shows an output signal to the recording section 4 and the display section 5.
An optical image inputted through the lens section 1 is outputted as a 24p imaging signal by the imaging section 2. As shown in FIG. 16(a), the imaging section 2 outputs the 24p imaging signal every ( 1/24) second in synchronization with the 24p vertical synchronizing signal. A method of outputting the signal includes a method of outputting the signal over a ( 1/24) second as indicated by FIG. 16(b) and a method of intermittently outputting the signal in a shorter time than a ( 1/24) second as shown in FIG. 16(c). Numbers in FIGS. 16(b) and 16(c) indicate the frame numbers of the 24p imaging signal. Diagonally shaded parts in FIG. 16(c) indicate no-signal output periods (blanking periods).
The method of FIG. 16(c) is applied to an imaging apparatus using a CCD (Charge Coupled Device). This is because when the CCD is used, a longer transfer time of accumulated charge seriously degrades picture quality and it is desirable to output (transfer) charge within a ( 1/30) second. The following will describe the case where the 24p imaging signal is outputted over a ( 1/30) second every ( 1/24) second according to the method of FIG. 16(c).
The photographed image state detecting section 7 detects a state of a photographed image, for example, an average value and a peak value of a luminance signal and a color-difference signal in each frame of the 24p imaging signal outputted from the imaging section 2 (FIG. 16(f)), and the photographed image state detecting section 7 outputs necessary control data (control signal) to the lens section 1 and the imaging section 2 based on the data (FIG. 16(g)). A frame 1:A, a frame 2:B, . . . of FIG. 16(f) indicate that a photographed image state A, a photographed image state B, . . . are detected from a frame 1, a frame 2, . . . . Further, control data A, control data B, . . . of FIG. 16(g) indicate that control data based on the photographed image state A, the photographed image state B, . . . is outputted from the photographed image state detecting section 7.
The memory section 3 performs the writing operation and the reading operation of FIGS. 16(i) and 16(j). That is, the memory section 3 writes the 24p imaging signal in a memory area (not shown) over a ( 1/30) second and performs 2:3 pull-down processing to convert two frames of the 24p imaging signal into five fields of the 60i signal. Then, the memory section 3 alternately reads an odd-numbered line (odd) and an even-numbered line (even) of the interlace signal every ( 1/60) second in synchronization with a 60i vertical synchronizing signal, and the memory section 3 outputs the signal to the recording section 4 and the display section 5 as a 2:3 pull-down signal. That is, the memory section 3 outputs the signal after converting, for example, frames 1 and 2 of the 24p imaging signal into 1-odd (hereinafter odd will be simply referred to as o), 1-even (hereinafter even will be simply referred to as e), 2-o, 2-e, and 2-o of the 60i signal.
The synchronizing signal generating section 6 outputs the 24p vertical synchronizing signal (FIG. 16(d)) and the 60i vertical synchronizing signal (FIG. 16(h)) to each section to cause the imaging apparatus to perform the operations.
However, in the conventional imaging apparatus, the 24p imaging signal is outputted from the imaging section over a ( 1/30) second every ( 1/24) second as shown in FIG. 16(c). The 2:3 pull-down signal is read from the memory section every ( 1/60) second as shown in FIG. 16(j). Thus, the output timing of the 24p imaging signal from the imaging section, that is, the writing timing of the 24p imaging signal to the memory section becomes different from the output timing of the 2:3 pull-down signal from the memory section, so that the writing operation of the 24p imaging signal may be started by the memory section 3 when the memory section 3 reads a signal around the center of one field. That is, the 24p imaging signal may be changed from a blanking period to an effective period during a reading operation of the 2:3 pull-down signal on a display position around a (½) field.
In this way, when the writing operation of the 24p imaging signal is started during the reading operation of the 2:3 pull-down signal on the display position of the (½) field, circuits in the memory section are varied in signal level because the 24p imaging signal changes from the blanking period to the effective period. Subsequently, a horizontal stripe caused by the difference in signal level appears around the display position of the (½) field, that is, around the center of a screen, thereby degrading picture quality.
Conventional configurations are applicable to the recording section and the display section for processing the 60i signal, whereas the photographed image state detecting section needs to process the 24p imaging signal and is mainly designed for processing the 60i signal. In this case, another circuit is necessary for the 24p imaging signal. Alternatively, when the circuit for the 24p imaging signal is shared for the 60i signal, the processing becomes complicated.
Another problem of 2:3 pull-down is that the frames of the 24p imaging signal are unevenly reproduced and result in jerky motions. This is because two frames of the 24p imaging signal are converted into five fields of the 60i signal and the frames are displayed with the same field like (2-o, 2-e) and (2-o, 3-e).
Further, a 24p imaging signal with a high vertical band is converted into a 60i signal, the 24p imaging signal having a vertical resolution nearly twice that of an image signal obtained with a field frequency of 60 Hz according to the interlace scanning method which is a standard television system. In this case, the vertical band of the aliasing signal of the 60i signal becomes a wide band, resulting in a larger flicker and lower visibility on a screen.